i) Technical Field of the Invention
This invention relates to a device and a method for controlling motor operation.
ii) Description of the Related Art
Currently, a feedback control is commonly used to control a motor which operates a carriage of a printer. In such a printer, it is necessary to accelerate the carriage to a predetermined speed, move the carriage at the predetermined speed in a section scanning a recording sheet, and then decelerate the carriage so as to stop the carriage at a predetermined stop position.
If the carriage is not accelerated to a target speed in an acceleration section where the carriage should be accelerated, and is not accurately moved at a certain speed in a constant-speed section where the carriage should be moved at the certain speed, a recording position onto the recording sheet cannot be settled. If the carriage does not accurately stop at the desired stop position in a deceleration section where the carriage should be decelerated, the recording position onto the recording sheet is shifted as the carriage is moved from then on. As a result, the quality at the time of recording onto the recording sheet (recording quality) is deteriorated.
Accordingly, it is desirable to use both the speed control which focuses on a traveling speed of the carriage in the acceleration section and the constant-speed section, and the position control which focuses on a position of the carriage in the deceleration section.
However, if the speed control and the position control are merely switched over, the manipulated variable to the motor becomes instantaneously destabilized at the time of switching the control. The traveling speed of the carriage is irregularly changed. Thus, recording quality may be lowered.
These days, various techniques are introduced to inhibit such irregular changes in the traveling speed of the carriage. For example, Unexamined Japanese Patent Publication No. 2001-63168 discloses a technique in which a manipulated variable to a motor is regulated (the control is performed by setting “0” to the positional error) at the time of the switching from the speed control (accelerating and constant-speed states) to the position control (decelerating state). Thus, an abrupt change in the manipulated variable to the motor is prevented.